1. Field of the Invention
This invention relates to a substrate processing apparatus, a substrate processing method, and a computer-readable storage medium which are adapted to laminate layers of resultants of mutually reactive gases to form a thin film on a substrate by performing a gas supply cycle which supplies the reactive gases sequentially to a surface of the substrate in a vacuum chamber.
2. Description of the Related Art
As a film deposition technique in a semiconductor fabrication process, a technique of forming a thin film is known which sequentially supplies at least two kinds of mutually reactive gas in a vacuum pressure atmosphere to a semiconductor wafer (also called a wafer) which is a substrate. Specifically, in this film deposition technique, a first reactive gas is supplied to and adsorbed by the surface of a wafer and subsequently a second reactive gas is supplied thereto, so that one or more atomic or molecular layers are formed on the wafer surface through the reaction of the two reactive gases. This gas supplying cycle is repeated multiple times (for example, several hundreds times). Such layers are laminated together to form a multi-layered thin layer on the surface of the wafer. This process is known as an atomic layer deposition (ALD) or a molecular layer deposition (MLD).
The above-described film deposition technique is advantageous over the conventional CVD (chemical vapor deposition) technique in that the film thickness can be controlled at a higher level of accuracy by the number of times of the gas supplying cycle and an excellent uniformity of the film within the surface can be attained, which is useful for the fabrication of semiconductor devices with a smaller film thickness.
Several devices which are arranged to perform the above-described film deposition process have been proposed as in Patent Documents 1 to 8 listed below. A description will now be given of a film deposition device of a typical type.
In a vacuum chamber of the film deposition device of the typical type, a turntable on which two or more wafers are mounted in a circumferential direction (a rotational direction) is arranged, and two or more gas supplying units to supply the first and second reactive gases to the wafers are arranged in the upper portions of the vacuum chamber to face the turntable.
The wafers are placed on the turntable, an internal pressure of the vacuum chamber is reduced to a predetermined processing pressure, and the wafers are heated and simultaneously the turntable and the gas supplying units are rotated relative to each other around a vertical axis. Moreover, the first reactive gas and the second reactive gas from the gas supplying units are supplied to the surface of each wafer respectively.
By arranging the separating walls between the gas supplying units or by blowing inert gas to provide an air curtain, the vacuum chamber is divided into a processing area formed with the first reactive gas and a processing area formed with the second reactive gas.
In this manner, the two or more reactive gases are simultaneously supplied to the vacuum chamber, and the processing areas are separated from each other to prevent the mixing of the first and second reactive gases on the wafers. The first reactive gas and the second reactive gas are sequentially supplied through the separating walls or the air curtain to each wafer on the turntable. Therefore, it is not necessary to replace the atmosphere in the vacuum chamber each time the kind of the reactive gas supplied to the vacuum chamber is changed. One of the reactive gases supplied to the wafer can be switched to the other quickly. The film deposition process can be performed by the above-described film deposition device speedily.
In the above-described film deposition device, a gas flow takes place on the wafer surface by a gas flow produced when the turntable and the gas supplying unit are rotated relative to each other in combination with a gas flow determined by the positional relationship between the gas supplying unit and the exhaust opening. In addition, the circumferential speed of the gas flow during the relative rotation of the turntable and the gas supplying unit varies depending on the position in the radial direction of the turntable. The uniformity of the gas flow in the surface of the wafer is lower than that in the normal vacuum processing unit of the single wafer type. Hence, although the ALD can inherently provide excellent uniformity of the film thickness in the surface, the above-described film deposition device may not be able to demonstrate the advantageous feature thereof sufficiently.
Moreover, with the use of minute patterns of semiconductor devices, good characteristics of the film for the embedding in the recesses as the patterns are demanded. For this reason, the approach to making the thin film flow is known which is arranged to perform, when the aspect ratio of a recess is high, an anneal processing after the thin film is formed by the CVD (Chemical Vapor Deposition) method and the recess is embedded therein, in order to fill the cavity internally formed therein.
However, in this approach, the anneal processing is performed after the thin film is formed and the recess is filled. In order to fill the cavity internally formed in the recess, a high heating temperature and a long processing time are needed. This process may result in a lowering of the throughput, and there may be a probability that a severe thermal history be given to the device structure which is already formed.
When the ALD method is performed, good embedding characteristics are provided inherently, but because the thin film is precise, it is difficult to obtain the fluidity of the thin film by the anneal processing. When the aspect ratio of the recess is high, or when the cross-section of the recess is in a reverse-tapered shape, the performance of the ALD method may produce a cavity in the embedded portion. In such cases, even if the anneal processing is performed, it is difficult to make the thin film flow. As a result, there is a probability that good embedding characteristics cannot be provided.
In addition, when performing the ALD method, it is necessary to efficiently reduce the impurities (such as organic substances) included in the thin film.
Patent Document 9 listed below discloses a method in which plural wafers are arranged in the circumferential direction on a disc, a rotary arm which supports the disc is rotated around its axis, and an ion beam is injected to each wafer on the disc during the rotation of the rotary arm in order to form a source area and a drain area on the surface of each wafer.
One fourth of the total amount of the ion beam injected is given to each wafer, and the wafer is rotated in the circumferential direction by 90 degrees. Subsequently, one fourth of the total amount of the ion beam injected is given again, and the wafer is further rotated in the circumferential direction by 90 degrees. While the wafer is rotated by 360 degrees, the total amount of the ion beam injected is given.
According to this method, ions can be uniformly injected to the transistors which are arrayed in various directions relative to the direction of the reciprocating linear movement of the disc. However, Patent Document 9 does not take into consideration the above-described problems of the film deposition device which is arranged to perform the ALD method.
Patent Document 10 listed below discloses a method in which, when forming a SiO2 insulation film by performing the ALD method, a Si source gas is supplied, then an ozone gas is supplied, and further a steam gas is supplied. However, Patent Document 10 does not take into consideration the above-described problems of the film deposition device which is arranged to perform the ALD method.
Patent Document 1: U.S. Pat. No. 6,634,314
Patent Document 2: Japanese Laid-Open Patent Publication No. 2001-254181
Patent Document 3: Japanese Patent No. 3144664
Patent Document 4: Japanese Laid-Open Patent Publication No. 04-287912
Patent Document 5: U.S. Pat. No. 7,153,542
Patent Document 6: Japanese Laid-Open Patent Publication No. 2007-247066
Patent Document 7: United States Patent Application Publication No. 2007/0218701
Patent Document 8: United States Patent Application Publication No. 2007/0218702
Patent Document 9: Japanese Laid-Open Patent Publication No. 05-152238
Patent Document 10: Japanese Laid-Open Patent Publication No. 2006-269621